[INFRA] Import NVIDIA/CCCL upstream as optimization reference library

CCCL (CUDA C++ Core Libraries) provides:
- CUB: device/block/warp-level GPU primitives (reduce, scan, sort, topk)
- Thrust: high-level parallel algorithms (transform_reduce, sort, scan)
- libcudacxx: CUDA C++ standard library (atomics, barriers, memory)
- cudax: experimental features (memory resources, allocators)
- Tuning policies: per-SM hardware-specific algorithm parameters

Competition optimization vectors mapped to CCCL:
- Output TPS (83% weight): warp_reduce, block_reduce, device_topk
- Input TPS (14% weight): device_scan, block_load, prefetch
- Cache TPS (3% weight): prefix caching strategy patterns
- Memory (0.9 util): pooled/cached/buddy allocators

Source: https://github.com/NVIDIA/cccl (shallow clone, HEAD only)
License: Apache-2.0

cccl_upstream/cub/test/test_cdp_variant_state.cu

@@ -0,0 +1,34 @@
+/*
+ *  Copyright 2022 NVIDIA Corporation
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+#include <cub/detail/detect_cuda_runtime.cuh>
+
+#include <cstdlib>
+
+int main()
+{
+  // This test just checks that RDC is enabled and detected properly when using
+  // the %PARAM% system to request CDP support (see the README.md file in
+  // this directory).
+
+  // %PARAM% TEST_LAUNCH lid 0:1:2
+
+#ifdef CUB_RDC_ENABLED
+  return (TEST_LAUNCH == 1) ? EXIT_SUCCESS : EXIT_FAILURE;
+#else
+  return (TEST_LAUNCH == 0 || TEST_LAUNCH == 2) ? EXIT_SUCCESS : EXIT_FAILURE;
+#endif
+}